1
Solar Cell
Access to this content is available to Ward's World readers for free
from McGraw Hill's AccessScience, an award-winning, digital STEM
resource that provides immediate, authoritative answers to students' thirst
for scientific knowledge on topics such as climate change, virology,
pollution, and more. Ward's World and McGraw Hill have partnered to
offer educators a no-obligation, free trial subscription to this product.
Request your free trial today and discover how valuable AccessScience
can be for you and your students.
A device that converts light energy directly to electrical
energy; also known as a photovoltaic (PV) cell. PV cells are
made of various semiconductor materials, such as silicon and
gallium arsenide. Solar cells may be used individually to power
small applications, such as calculators, or connected in series
and parallel as modules or panels to obtain the required values
of current and voltage for electric power generation (Fig. 1).
Connecting solar cells in series increases the voltage; connect-
ing them in parallel increases the current. Modules may be
grouped in parallel or strung in series to form PV arrays.
Photovoltaic effect
The conversion of sunlight into electrical energy, or the pho-
tovoltaic effect, involves three major processes: absorption of
the sunlight in the semiconductor material; generation and
separation of free positive and negative charges to different
regions of the solar cell, creating a voltage in the solar cell; and
transfer of these separated charges through electrical terminals
to the outside application in the form of electric current. In the
first step, the absorption of sunlight by a PV cell depends on
the intensity and quality of the sunlight, the amount of light
reflected from the front surface of the solar cell, the semicon-
ductor band-gap energy [which is the minimum light (photon)
energy the material absorbs], and the layer thickness.
Some materials such as silicon require tens of micrometers of
thickness to absorb most of the sunlight, while others such as
gallium arsenide, cadmium telluride, and copper sulfide require
only a few micrometers.
+
ward
'
s
science
Key Concepts
• Solar cells, also known as photovoltaic (PV) cells, are devices that convert light energy directly to electrical energy.
• A solar cell consists of a semiconductor material (such as silicon), an electrical junction, and electrical terminals
to conduct electric current.
• Energy conversion in a solar cell involves three major processes: light absorption in the semiconductor material;
generation and separation of charges to create a voltage; and transfer of these charges through terminals to the
outside application.
• When light is absorbed in the semiconductor, a negatively charged electron and positively charged hole are created.
The electrical junction separates these electrons and holes from one another.
• Connecting solar cells in series increases the voltage; connecting them in parallel increases the current.
Fig. 1: Photovoltaic panels utilizing solar cells to turn sunlight into renewable electrical power.
(Credit: iStock.)
